It is difficult to overstate human impact on the Earth's life-support systems. All living organisms depend on the world's net primary productivity -- the energy trapped by the world's green plants via photosynthesis. Renewable energy resources are being consumed by humans out of proportion to its own needs and the quota required by other living beings and at a rate greater than natural replacement. Current energy use practices are also degrading the environment at unacceptable levels.
The world's non-renewable energy resources, notably fossil fuels, are also being rapidly depleted. This is due to the accelerating energy requirements made by rapid global population growth and development. It is predicted that certain regions of the world will consequently face increasing energy shortages. Wasteful and inefficient energy use practices are a significant contributor to energy exhaustion. For instance, some of the fastest population growth is occurring in countries dependent mostly on fuelwood, facilitating its unsustainable consumption by deforestation.
In 1994, OECD reported that there has been a general increase in total energy consumption of 30 percent over the past 20 years. By 2010, OECD countries are expected to be consuming 30 percent more energy and nearly 20 percent more oil than in 1990.
An analysis by IIASA of different types of electric light bulbs took into account the total energy consumption and costs of every stage in the electricity supply chain: the fuel extraction and supply, electricity generation, electricity transmission, and running the light bulb itself. It found that costs to deliver the same service could differ by about 30%, while carbon dioxide emissions to provide that service could differ by more than 90% and primary energy use by 75%. For example, per lumen-year, a standard incandescent bulb, powered by electricity from a conventional coal-fired power station in the USA, cost only fractionally more than a compact fluorescent bulb four times its purchase price, but run from a modern combined-cycle natural gas turbine with carbon scrubbing. The compact fluorescent bulb had 25% of the primary energy demand of the incandescent bulb and less than 10% of its carbon dioxide emissions. So cost savings bore little relationship to environmental and resource savings. In addition, the differences in energy consumption were almost entirely on account of the different bulbs, whereas the carbon dioxide savings were divided between the effect of cleaner fuel and the more energy efficient light bulb.
The modern industrial economies of North America, Europe and parts of East Asia consume immense quantities of energy and raw materials, and produce high volumes of wastes and polluting emissions. The magnitude of this economic activity is causing environmental damage on a global scale (notably climate change) and widespread pollution and disruption of ecosystems, often in countries far removed from the site of consumption. Considerable progress has been made in controlling pollution at local and transboundary levels in the wealthier industrialized countries but the wider-scale impacts have yet to be tackled effectively.
It is important to distinguish between the efficiency of the individual technology and the efficiency of its use or the system. Most Russians travel with public transport; Russian buses are less efficient than German buses, but they are more efficient movers of people than German cars. Efficiency gains in individual technologies may be offset by the decentralization of energy systems and the shift away from collective structures of energy end-use. Replacing a common, hot water system in an old apartment block with new individually-powered, thermostatically-controlled radiators may save energy on the one hand through finer control of individual heating requirements, but may be overall less efficient than linking up the old system to a source of cogeneration or district heating plant.